For over fifty years heavy haul railroads have used a variety of methods to reduce friction between the rail vehicle wheel flanges, and the gauge face of the rail with which it comes in contact. Railroads and transits have realized they can save substantial amounts of money in lowered maintenance and equipment replacements if lubrication is applied.
There have been many attempts to develop formulations to provide lubrication to rolling/sliding elements such as wheel/rail contact in railroads, particularly where the track curves, a location where the greatest friction between the gauge face and wheel flanges is to be expected. These formulations range from liquid and grease systems, which generally require more expensive application equipment, frequent monitoring and suffer from plugging applicators which limit effectiveness and reliability, to solid stick formulations.
A first method utilizes hundreds of wayside lubricators that eject hydrocarbon petroleum based lubricants onto the gauge face of the rail as the train travels, particularly at curves in the track.
A second method for applying lubricant has been to use track inspection trucks to spray petroleum and/or synthetic grease onto the gauge face of the track as the inspection truck goes around the curve in the track.
A third method is to apply lubricant to the wheel flange of the locomotive, whereupon the lubricant is transferred from the wheel flange of the locomotive to gauge face of the track, and to the wheel flange of the railcars being pulled by the locomotive, the lubricant being passed back through the train as successive wheels come in contact with the rail and pick up some of the lubricant.
These types of lubrication are typically accomplished by spray devices that squirt small amounts of lubricating oil onto wheel flanges. There are inherent problems with the above-described methods of applying lubricant to a gauge face. First, sprayed oil has a tendency to migrate to the tread of the wheel, making it more difficult for the train to stop. Second, lubricants on top of the rail can cause the train wheels to slip, inhibiting the ability of the brakes of the train to slow or stop the train. Further, lubricants (e.g., grease, oil) on top of the rail can make it difficult for the train to gain traction from a stopped position, or when climbing an incline. Finally, to keep oil spray devices in working order, excessive maintenance of the devices is required, costing additional time and expense to the railroad.
An alternative lubrication method which overcomes some of the problems inherent in spraying oil onto the wheel flange of the locomotive has been to use a solid lubricant stick or rod (herein “lubricant stick”). The lubricant stick is inserted into a tube that is then applied by various mechanical means to the flanges of the wheel of a rail vehicle via friction. In such prior lubricant sticks, the lubricant is embedded within a polymeric carrier (typically a petroleum based polymer such as polyethylene). The lubricant stick is pressed against the wheel flange for wearing off, and application of lubricant there-to.
Solid stick formulations, such as those disclosed in U.S. Pat. Nos. 3,537,819, 3,541,011 & 3,729,415 (Davis, et al.) focus on the use of a high molecular weight polyethylene to control lubricant deposition; U.S. Pat. No. 4,915,856 (Jamison) discloses a thermoplastic stick formulation which contains lead and other potentially hazardous metallic powders; U.S. Pat. No. 6,649,573 (Mitrovich) highlights a thermoplastic polymer (various density polyethylene), and a mixture of organic and inorganic extreme pressure additives; and U.S. Pat. No. 7,709,426 (Eadie, et al.), discloses a solid stick composition comprised of a thermosetting resin and a grease. All of these lubricant stick formulations are generally comprised of a non-biodegradable, hydrocarbon-based (polymer) binder, a hydrocarbon grease or oil, and various solid lubricants combined in such a manner that the finished product is in a solid form which is easily handled. These materials are then applied to surfaces requiring lubrication, typically an open journal such as the wheel flange, or tread of a rail wheel. These lubricant sticks are consumed as the rail vehicle moves down the track, and all of the materials contained in the lubricant sticks are dispersed along the rail bed as the rail vehicle progresses.
One prior patent, U.S. Pat. No. 7,943,556 (Mitrovich), discloses environmentally friendly lubricant compositions utilizing a polylactic acid—based polymer such as polyactide (PLA). Environmentally friendly lubricants are desirable because they minimize or eliminate any potential damage to the environment.